Rheostat



June 28 1927.

w. s. SUTTON RHEOSTAT' File d Oct. .21, 1922' Patented June 28, 1927.

UNITED? STATES PATENT ()FFICE.

, WILLIAM S. SUTTON, OF ROCKFORD, ILLINOIS.

RHEOSTAT.

This invention pertains generally to radio or wireless-transmission, or reception, and has more particular reference to a rheostat adapted :to adjustably supply current to the filament of a vacuumctube, and may be em- StatlODc In the operation of a vacuum tube,

it i'is'svery'desirable toTsupply the filament current through a control means that is capable oft ver y fine and gradualadjustment lIlOIClBIEtO secure maximum efficiency of the tube; y

The resistance coils,;customarily employed for the purpose indicated, have prior towmy invention comprisedda! series of convolutions connected at intervals to contact point; adapted to be individually engaged by an adjustable switch or contact member. The effective resistanoe of such: a coil could therefore-beivaried only in steppedintcrvais limited as-to finenessby the total resistance of said convolutionsi cuti intone! out of the circuit, and consequently only anrapproximation of accuracy' could be secured with coilso'f :this character; I I

One of the primary objects of my present invention is top-rovide a rheostat, which will be capable of substantially infinitesimal adjustments to varythe effective resistance by minute gradations, so that extremely fine and very accurate resistance variations can be ob tained; p p

' A further object ofthis invention is to provide a resistor of the proper proportions and a contact shoe adapbed tomake sliding; contact with said resistor, the parts being; so

arranged with relation to each other that they maybe mounted in a conveniently'small space; and operated from" knobs in the center of 'thedevice; one knob furnishing roughly? the approximate resistance, while the other knobprovides vernier or fine adjustment for securing a very "close and accurate supply of current=to thefilament.

Another object of th'einvention is theprovisionoi 'a rh'eostat Which Will be siniple,, but

substantial and durable inconstruction; one

Applicationflled October 21, 1922. Serial No. 595,974.

which can be economically manufactured. and which will be ef icient, accurate and re liable in operation.

Other objects and advantages of this invention should bereadily' appreciated by those skilled inthe art a the same becomes better understood by reference to the following description wh ii considered in connection with the eccoi'npanyinp; drawings.

Referring to the drawings: l

Figure 1 is a medial; sectional view through a rh'eostat embodying my invention; 2 is a fragmentary face view. showing the adjusting knobs;

Fig. 3 is a sectional view on the line 33 of Fig. 1;-

Fig'. 4 is; a sectional view on the line 4-4 of Fig. 1; and V Fig. 5 is a detailed sectional view through the contact element taken on the line 5-5 of Fig".

Referring: now to the drawings more in detaih reference character 6 indicates generally the front panel of the cabinet in which the various apparatuses of a receiving station are mounted. To the rear or inner face of this panel. there is secured a housing comprising a plate 7 and shell 8 secured to the panel by a plurality of screws 9, or other preferred fastening means. I

lVithin this housing is rotatably mounted the resistance coil, which comprises a series of convoliti'tions 11 wound in spaced relation upon a cylinder or drum 12' made of suitable insulating mat-eriaand connected by a web or spider 13 to a pinion 14 which is rigidly attached to shaft 15, journaled at one lid in a suitable and preferably insulated bushing 16, and projecting at its other end forwardly of the panel 6, where an operating knob 17 is mounted thereon.

One end of the coil 11 is connected to the web 1305 the cylinder as indicated by reference character 18 and'the other end is embedded in or otherwise fixedly anchored to the insulated portion 12 of the cylinder. A binding post 19 projects at the rear of the shell S'for the attachment of one of the'circuit wires thereto, while its inner end is equipped with a spring wiper or contact member 521 continuously contacting the web 13 of the cylinder, the binding post being mounted in an insulati bushing 22, as shownin Fig. 1, upon the periphery of the casing 8. A. second binding post 28 is mounted in an insulating bushing 2 and upon the inner end of this post within the shell there is pivotally mounted a leaf spring contact member 25, extending circumferentially a limited distance around the cylinder 12, and being equipped at its free end with a wiper or brush 26 provided with a groove 2? as shown in Fig. 5, which is adapted to straddlc the resistance wire 11, making a good conducting contact therewith, and maintaining the brush and member 25 against accidental displacement from the wire. It will be manifest that when the wires of the circuit are connected to their respective binding posts 19 and 23, the current will flow through so much of the coil as is included between the'end 18 attached to the web 13 of the cylinder and that point on the coil which is engaged by the brush 26, by which the current is taken from the coil at this point and carried through the member 25 to the binding post n8. It will also be obvious that the length of that portion of the resistance coil included in the circuit may be varied by rotating the cylinder and thereby the coil, thus varying the effective resistance of this coil.

The mechanism by which the rotative ad justing movement of the cylinder is effected will now be described:

Upon the interior of the shell 8 there is fixedly mounted an internal ring gear 28 disposed in radial alignment with the pinion lt and between this internal gear and the pinion there is interposed a gear 29 meshing with both the internal gear and the pinion, as shown in Fig. 4;, and rotatably mounted through the instrumentality of a stub shaft 31 upon an arm 32, the hub 33 of which is rotatable about the shaft 15 and within a bearing opening 34 formed in the plate 7. A circumferentially knurled knob 35, also rotatably carried by the shaft 15, has a dove tailed connection with the hub 33 of the arm 32, as indicated at 36 (Fig. 1). For purposes of determining the relative position of the knob 38 it is preferably equipped with an indicator or pointer 37, adapted to cooperate with the indices (not shown) suitably positioned on the outer face of the panel 6.

In the operation of my invention the rough or primary tuning is effected by manipulation of the knob which rotates the arm 32 about the shaft 15, and by reason of the interineshing relation of the gear 29 with the rotatable pinion 14c and the stationary internal ring gear 28, this pinion and consequently the cylinder 12 and the coil carried thereby. are rotated at a greater speed than the rotation of the knob When by this adjustment the effective resistance of the coil has been brought to an approximation of tha desired. the final adjustment is secured by slowly manipulating the knob or button 1?, which, being directly connected with the cylinder, moves the cylinder slowly, thus enabling a final accurate adjustment to a fine degree of nicety, which results in accurate regulation of the circuit.

It should be apparent, therefore, that with my improved rheostat, extremely fine gradations of adjustment can be securec, which will result in absolute accuracy of control, such as is incapable of attainment by instruments which necessitate a step-by-step adjustment and are wholly incapable of any variation of resistance between the successive steps.

It is believed that my invention and many of its attendant advantages will be understood from the foregoing without further description, and while I have shown and described a preferred embodiment of the invention, obviously it is capable of a wide variation in its construction, without departing from the essence of the invention as defined in the following claims.

I claim:-

I. In an instrument of the character described the combination of a casing, a shaft mounted therein having an element thereon to be rotated therewith in fine and coarse gradations of adjustment, an adjusting knob fixed to said shaft to communicate direct adjustment to said element, an arm rotatably mounted on the shaft, an operating knob connected to said arm, a gear carried by the arm, a pinion fixed with respect to said ad j ustable element and meshing with said gear, and an internal gear mounted in said casing and meshing with said first mentioned gear, said last mentioned knob being aranged to communicate adjustment to said element in directly through the transmission recited.

2. In a rheostat the combination of a rotatably mounted resistance coil, a contact member adapted to engage therewith, a primary means for rotatably adjusting said coil relatively to said contact member, comprising a manually operable knob and a plane tary step-up transmission between said knob and said coil, said planetary transmission having the planet element thereof moved through its orbit by said knob, and a final means for rotatably adjusting said coil, comprising a knob directly connected with said coil.

3. In a rheostat the combination of a housing, a resistance coil rotatably mounted therein, a contact member mounted on said housing and adapted to contact said coil and to follow the convolutions thereof upon rotation of the coil, means for rotatably adjusting said coil, comprising a pinion fixed with respect to the coil, an internal gear, a gear interposed between said internal gear and said pinion. and a manually operable means for revolving said gear about the axis of said coil, and a second manually operable device directly connected to said coil.

4. In a rheostat the combination of a casthe shaft, an operating knob connected to ing, a shaft mounted therein, a resistance said arm, a gear carried by the arm, a pincoil carried by said shaft, a movably mountion fixed With respect to said coil and mesh- 10 ed contact member adapted to engage with ing with said gear, and an internal gear 5 and follow the convolutions of said coil upon mounted in said housing and meshing With rotation of the coil, an adjusting knob fixed said first mentioned gear. to said shaft, an arm rotatably mounted on WILLIAM S. SUTTON. 

